Math Through Answer

$a$
$f(x) = 3x + 7$
f(x) = 3x + 7
Let $f$ be the function defined by $f(x) = 3x + 7$, and
let $a$ be a positive real number.
http://www.maths.tcd.ie/~dwilkins/LaTeXPrimer/MathMode.html

$a/b$
$\sqrt[3]{x+y}$
\frac{num}{den}
$\frac{1}{2}$
$a + b= c$
$\frac{w+a}{d+3}=\frac{r}{t}$
$\cos^2 x +\sin^2 x = 1$
\[\LaTeX\]
\frac{1}{2}